U.S. patent number 4,979,113 [Application Number 07/346,128] was granted by the patent office on 1990-12-18 for automated vehicle control.
This patent grant is currently assigned to The General Electric Company, plc. Invention is credited to Malcolm T. Roberts, Michael P. Robins, Ian E. Sharrott.
United States Patent |
4,979,113 |
Roberts , et al. |
December 18, 1990 |
Automated vehicle control
Abstract
A vehicle guidance system includes a computer for generating
signals to control a number of vehicles to carry out movements
within a predetermined area. Data identifying locations of notional
points on the floor of the area are entered into the computer
together with a look-up table specifying pairs of those points
between which movements of vehicles may be required, and specifying
which other of the movements between pairs of points must be
considered as potential causes of collision between vehicles when
any particular movement is to be effected. When a vehicle movement
is requested, the computer determines from the table which other
movements must be considered, and determines whether any such
movements are being effected at that instant. If so, the computer
inhibits the requested vehicle movement or, if not, it initiates
the requested vehicle movement.
Inventors: |
Roberts; Malcolm T. (Oadby,
GB2), Robins; Michael P. (Rugby, GB2),
Sharrott; Ian E. (Stoney Stanton, GB2) |
Assignee: |
The General Electric Company,
plc (GB2)
|
Family
ID: |
10636903 |
Appl.
No.: |
07/346,128 |
Filed: |
May 2, 1989 |
Foreign Application Priority Data
|
|
|
|
|
May 13, 1988 [GB] |
|
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8811441 |
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Current U.S.
Class: |
701/24; 318/587;
701/301; 180/168 |
Current CPC
Class: |
G05D
1/0282 (20130101); G05D 2201/0216 (20130101); G05D
1/0289 (20130101) |
Current International
Class: |
G05D
1/02 (20060101); G06F 015/50 () |
Field of
Search: |
;364/424.01,424.04,449,461,424.02 ;180/167-169 ;340/988,989
;318/587 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Chin; Gary
Attorney, Agent or Firm: Kirschstein, Ottinger, Israel &
Schiffmiller
Claims
We claim:
1. A method of operating a vehicle guidance system which includes
computer means for generating signals to control a plurality of
vehicles to execute movements over a floor within a predetermined
area, the method comprising the steps of: entering into said
computer means data identifying locations of notional points on the
floor of said area; entering into said computer means a look-up
table which specifies a plurality of pairs of said points for each
of said pairs a vehicle movement will be required between one point
and the other point of said pair, and said look-up table also
specifies, for each said required vehicle movement, other pairs of
said plurality of pairs of points which define vehicle movements
which must be considered as potentially resulting in collision with
a vehicle making said required movement; generating a signal for
requesting movement of a first vehicle between a first said pair of
points; and, when said movement of said first vehicle is requested,
said computer means determining from said table which potential
collision movements must be considered, and determining whether any
vehicle is carrying out any of said potential collision movements
and, if so, inhibiting said requested movement of said first
vehicle and, if not, initiating said requested movement of said
first vehicle.
2. A method as claimed in claim 1, wherein coordinates of
intermediate points along a path to be steered by said first
vehicle in moving between said first pair of points are stored; and
wherein when said first vehicle is moving along said path, movement
of another vehicle along a second path adjacent said intermediate
points is inhibited by the computer means.
3. A method as claimed in claim 2, wherein respective sets of said
coordinates of intermediate points are stored for different paths
between said first pair of points; and wherein a particular one of
said sets is selected in dependence upon dimensions of said first
vehicle.
4. A vehicle control and guidance system, comprising: computer
means for generating signals to control a plurality of vehicles to
execute movements over a floor within a predetermined area, and
operative for storing data identifying locations of notional points
on the floor of said area; means operable by a user of the system
for entering into the computer means a look-up table which
specifies a plurality of pairs of said points for each of said
pairs a vehicle movement will be required between one point and the
other point of said pair, and said look-up table also specifies,
for each required vehicle movement, other pairs of said plurality
of pairs of points which define vehicle movements which must be
considered as potentially resulting in collision with a vehicle
making said required movement; and means for requesting movement of
a first vehicle between a first said pair of points; said computer
means being operative, when said movement of said first vehicle is
requested, to determine from said table which potential collision
movements must be considered, and to determine whether any vehicle
is carrying out any of said potential collision movements, and, if
so, to inhibit said requested movement of said first vehicle and,
if not, to initiate said requested movement of said first vehicle.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the control of automated vehicles which
move around a site, such as a factory or a warehouse, in accordance
with control signals generated by a computer. The invention is
particularly relevant to vehicles which are controlled over radio
or other remote control links and do not rely on guidance wires or
tracks.
2. Description of Related Art
Our British Patent No: 2,143,395 discloses such a system in which a
number of mobile trucks are controlled and guided under the overall
control of a base station. The trucks are utilised to transfer
material between a store area and a work position. Finished
work-pieces are transferred by means of one of the trucks to a
holding area for removal and utilisation as required. The base
station allocates destinations to each of the trucks via a
communication link, such as a radio or infra-red link.
Each vehicle is able to determine its own position relative to any
location within the site. Each vehicle monitors its own position as
it moves along a path to its required destination, and continuously
transmits its position back to the base station, so that the base
station can control the truck movements so as to avoid
collisions.
Typically the storage area, the work position and the holding area
may each comprise a large number of bays divided into separate
sections by aisles along which the trucks must travel.
A possible way to prevent collisions between vehicles in such a
system, is for the computer controlling the vehicles to store the
positions of zones which only one vehicle is allowed to occupy at a
time, and to ensure that if a vehicle has been instructed to move
into a zone no other vehicle can approach or enter that zone. It
will be apparent that such a mode of operation limits the
efficiency of the system, as much time can be wasted while vehicles
are waiting to move.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a vehicle control
system by which such waiting time can be reduced.
According to one aspect of the invention there is provided a method
of operating a vehicle guidance system which includes computer
means for generating signals to control a plurality of vehicles to
execute movements within a predetermined area, the method
comprising the steps of: entering into the computer means data
identifying locations of notional points on the floor of said area;
entering a look-up table specifying pairs of such points between
which movements of vehicles may be required and specifying which
other of said movements between pairs of points must be considered
as potential causes of collision between vehicles when any
particular movement is to be effected; and, when a vehicle movement
is requested, causing the computer means to determine from the
table which other movement or movements must be considered, and to
determine whether any such other movement is being effected and if
so to inhibit the requested vehicle movement and if not to initiate
the requested vehicle movement.
According to another aspect of the invention there is provided a
vehicle control and guidance system comprising computer means for
generating signals to control a plurality of vehicles to execute
movements within a predetermined area and operative to store data
identifying locations of notional points on the floor of said area;
and means operable by a user of the system to enter into the
computer means a look-up table specifying pairs of said points
between which movements of vehicles may be required and specifying
which others of said movements between pairs of points must be
considered as potential causes of collision between vehicles when
any particular movement is to be effected; the computer being
operative, when a vehicle movement is requested, to determine from
the look-up table which other movement or movements must be
considered and to determine whether any such other movement is
being effected and if so to inhibit the requested vehicle movement
and if not to initiate the requested vehicle movement.
By use of the concept of notional points and the look-up table,
vehicle movements can be defined between relatively closely-spaced
points and, provided that there is no vehicle at present executing
a movement between two specific points, any vehicle may be
instructed to travel between those points or to travel close to or
crossing a notional line joining those points, without fear of
collision.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described, by way of
example, with reference to the accompanying drawings, in
which:-
FIG. 1 is a schematic block diagram of vehicle control and guidance
apparatus,
FIG. 2 is a schematic plan of an example of a warehouse around
which guided vehicles move under computer control,
FIG. 3 shows, on an enclosed scale, a region of the plan of FIG. 2,
illustrating vehicle movements,
FIG. 4 is a schematic plan view illustrating vehicle movements at a
T-junction, and
FIG. 5 illustrates the docking of a vehicle in a garage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a controller 1 for controlling the movement of
vehicles such as the vehicles 2 and 3 around the floor 4 of a
warehouse comprises a computer 5 which generates vehicle control
signals which are fed to a radio transmitter 6. The signals are
used to modulate a carrier wave which is transmitted via an antenna
7 and is received by antennas 8 and 9 on the vehicles 2 and 3. Data
are fed into the computer 5 from data input means 10 which includes
a radio receiver which receives position data from the vehicles 2
and 3 via an antenna 11. The data may alternatively be transmitted
by other means, such as via an ultrasonic or laser link. The data
input means may also comprise sensors for automatic sensing of
conditions within the warehouse, and a keyboard 12 is provided for
manual data entry.
For the sake of example, the navigating system of the vehicles is
taken as being as described in our above-mentioned British Patent
No: 2,143,395, but it will be appreciated that the present
invention could equally well be used with any other navigation
system. For navigation purposes, coded retro-reflective targets 13
are positioned, wherever necessary, around the warehouse. Rotary
laser scanners 14, 15 are fitted on the vehicles 2 and 3,
respectively, and the navigation system continuously determines,
from reflections from the coded targets, and by triangulation, the
exact position of each vehicle.
FIG. 2 illustrates, schematically, a plan of the warehouse showing
storage bays 16 to 22, each with docking points a to d at which
goods are loaded and unloaded. The bays are reached from aisles 23
to 29. In the past it would have been necessary to ensure that two
vehicles could never simultaneously enter any aisle.
In the present invention, however, notional "pads" are defined at
each docking point by determining their coordinates relative to a
datum position, such as the corner 30. These pad coordinates are
stored in the computer 5. In order to prevent collisions, the
supervisor of the warehouse enters, via the keyboard 12, a look-up
table which specifies pad designations at the ends of every vehicle
movement which may be required. For example, a vehicle may have to
move from the docking point (DP) 18d to the DP 17b, and another
vehicle from the DP 21c to the DP 16b, and so on. The supervisor
then enters into the table the end pad designations for all of the
movements which could conflict with each required movement in such
a way that there could be a collision if vehicles were to carry out
the movements simultaneously. Details of an example of a portion of
such a table will be described later. When the data input means 10,
or the program in the computer 5, commands a vehicle movement, the
computer determines, from the look-up table, which other movements
must be considered and, if such another movement is already being
carried out by a vehicle, inhibits the required movement until the
conflicting movement is completed. On the other hand, if no such
conflicting movement is in progress, it allows the required
movement.
It will be apparent, therefore, that instead of confining vehicle
movements to unoccupied aisles, the invention allows simultaneous
movements in any aisle provided that the movements are not
conflicting movements as designated by the look-up table. Greatly
improved efficiency of vehicle operation is thereby achieved.
FIG. 3 shows a region 31 of the layout of FIG. 2 in greater detail,
to illustrate the derivation of the look-up table. Considering
vehicle movements within that region, a vehicle movement A from the
DP 19b to the DP 16d, a movement B from the DP 17c to the DP 16a, a
movement C from the DP 16d to the DP 17d, a movement D from the Dp
18a to the Dp 18c, and a movement E from the DP 17c to the DP 18b,
(together with others which will not be detailed for the sake of
clarity of this example) might be required in that region.
The supervisor would enter the end pad designations for those
movements into the look-up table and would then consider each other
required movement to determine whether a collision situation could
occur. For example, considering the movement A, the only other
movement which could cause a collision would be the movement B. The
movement C could be in conflict with the movements A and D, whilst
the movement D could be in conflict with the movements C and E and
possibly with the movement B, depending upon the width of the
vehicles and the spacing between the pad positions for adjacent
docking points. The look-up table would therefore be built up as
follows.
______________________________________ End Pad End Pad Designations
Designations Required for Conflicting for Movement Docking Points
Movements Docking Points ______________________________________ A
19b-16d B 17c-16a B 17c-16a A 19b-16d D 17d-18b E 18a-18c C 16d-17d
A 19b-16d D 17d-18b D 17d-18b B 17c-16a C 16d-17d E 18a-18c E
18a-18c D 17d-18b B 17c-16a ______________________________________
and so on
The "pad" concept could be extended to take into account the
coordinates of points through which a vehicle is to pass without
stopping. Such points could be designated points along any required
vehicle route, such as shown in FIG. 4. In that case, a vehicle 32
pulling a trailer 33 is to move along an aisle 34 to a T-junction,
and there turn left into an aisle 35. Due to the overall length of
the combined vehicle and trailer, the vehicle must swing out as it
turns left, and the computer causes the vehicle to deviate from a
straight line along a path defined by points such as the points
36-42, the coordinates of which are known to the computer. A
vehicle 43 could be travelling in the opposite direction along the
aisle 35, and, if both vehicles were allowed to continue, a
collision could occur at or near the point 40. If points 44 and 45
are designated along the path of the vehicle 43, just outside the
potential collision area, the computer can ensure that if the
vehicle 32 and the trailer 33 are moving between the points 36 and
42, the vehicle 43 cannot move between the points 44 and 45, and
vice versa. A further set of points 46-50 could be designated along
a path of smaller deviation, for use when the vehicle 32 is
travelling without the trailer 33.
Similarly, a vehicle could be directed into a docking point with a
correct heading by using the "points" concept. FIG. 5 shows a
docking point 51, such as a garage, into which a vehicle 52 is to
be moved from a docking point 53. The vehicle must enter the garage
accurately within the doorway, and at the correct angle, to avoid
colliding with the garage walls. Points 54-56 are designated along
the required path for correct entry of the vehicle. The vehicle's
navigation system is commanded by the computer to direct the
vehicle from the point 54 at the required heading to reach the
point 55. The path to be followed thereafter to bring the vehicle
to the required heading to enter the garage along a path 57 is
derived by a splining operation.
Alternative sets of "pads" may be overlaid along any particular
route, to take account of the length and/or width of the vehicle to
be moved, different sets being allocated to different types of
vehicle. For example, one set could be allocated to a vehicle
towing a trailer and another set to a vehicle without a
trailer.
If any new movement between pads and/or points is required, the
data for effecting such movement, and the data relating to
potential collision movements, can readily be added to the look-up
table by the supervisor at any time.
* * * * *